simple tweak to meta::function and meta::nary_expr so that the pass_through transforms works on vararg patterns

[SVN r36850]

libs/xpressive

@@ -1 +1 @@
-Subproject commit 488f26138c8a08c7a07302a302651d682762f160
+Subproject commit 592692fe92f8ce8c544087120d6aa1076cf36da2